Display devices such as PDPs (plasma display panels) comprise: a front panel having electrodes, a dielectric layer and others on a transparent insulating substrate (such as a glass substrate); and, facing the front panel, a back panel having electrodes, a dielectric layer, barrier ribs, phosphors, and others on another transparent insulating substrate. And, the periphery of the two panels is sealed airtight. After or during the sealing process, the space between the two panels is evacuated and a discharge gas is introduced into this space. By contrast, in field emission type and electron emission type displays, the space between the front and back panels needs to be maintained in a high vacuum, and therefore air tightness along the periphery of the two panels is more vital.
In display devices such as PDPs as described above, glass compositions which soften at relatively low temperatures are used to form various parts such as the electrodes, dielectric layer and barrier ribs, and are also used as a sealant to seal the display panel. For example, coating members containing a glass composition that softens at about 550° C. are used to form the dielectric layer. Such a dielectric layer is formed by applying a glass paste over the electrodes on the glass substrate using screen printing or the like, followed by drying and heat treatment.
To seal the display panel, sealing members (sealants) containing a glass composition which softens at a temperature lower than about 500° C. are often used. Conventionally used sealants are glass compositions prepared by mixing a glass containing lead oxide as a major constituent and a filler. The sealing process includes the steps of: applying a glass paste along the periphery of the front or back panel and drying the applied glass paste; pre-firing the dried glass paste in an air atmosphere; embedding the front and back panels in a predetermined positional relationship to each other; and heating the pre-fired glass while evacuating the space between the two panels to complete the sealing process. Typically, the glass paste is applied using a printing or dispenser technique.
Currently, most PDPs employ an alternate current (AC) drive system. In the AC drive systems of PDPs, images are displayed by utilizing wall charges generated on the surface of the dielectric layer. Such systems have a problem in which part of the wall charges tend to remain on the surface of the dielectric layer after displaying an image, and such residual wall charges are prone to locally accumulate, thereby possibly triggering an abnormal discharge. In order to prevent such an abnormal discharge, Patent Literature 1 (JP-A 2000-348630) discloses a method for removing the above-described residual wall charges from the surface of the dielectric layer by using, as the dielectric layer, an electrically conductive glass that contains vanadium and has an electrical resistivity of 107 to 1015 Ω·cm.
In these years, the use of lead-containing materials is increasingly restricted for environmental considerations. Accordingly, various lead-free glass compositions for sealing or coating purposes are being proposed. For example, Patent Literature 2 (JP-A Hei 10(1998)-139478) and Patent Literature 3 (JP-A 2006-169047) disclose a glass composition containing bismuth oxide as a major constituent. Patent Literature 4 (JP-A Hei 7(1995)-69672) discloses a glass composition containing tin oxide as a major constituent. Patent Literature 5 (JP-A 2007-182347), Patent Literature 6 (JP-A 2006-342044) and Patent Literature 7 (JP-A 2008-185852) disclose a glass composition containing vanadium oxide as a major constituent.
Patent Literature 1: Japanese Patent Laid-open No. 2000-348630
Patent Literature 2: Japanese Patent Laid-open No. Hei 10(1998)-139478
Patent Literature 3: Japanese Patent Laid-open No. 2006-169047
Patent Literature 4: Japanese Patent Laid-open No. Hei 7(1995)-69672
Patent Literature 5: Japanese Patent Laid-open No. 2007-182347
Patent Literature 6: Japanese Patent Laid-open No. 2006-342044
Patent Literature 7: Japanese Patent Laid-open No. 2008-185852